1. Field of the Invention
The present invention relates to a control device for an internal combustion engine which transmits output to a drive-train via a dual mass flywheel.
2. Description of the Related Art
A technique is known that a dual mass flywheel is used to inhibit torque fluctuation of an internal combustion engine from being transmitted to a drive-train (see, for example, Japanese Patent Application Publication No. 2005-54601 (JP-A-2005-54601) and Japanese Patent Application. Publication No. 2006-183484 (JP-A-2006-183484)). The dual mass flywheel includes two flywheels that are connected together by an elastic body such as a spring. Therefore, the dual mass flywheel has a resonance frequency. If resonance occurs, it causes a large oscillation amplitude between the two flywheels. This may result in a shock due to an impact with the spring.
To inhibit such resonance of the dual mass flywheel, the resonance point is normally set at an engine speed range that is lower than the idling speed. However, the engine speed temporarily becomes lower than the idling speed depending on the operating state of the internal combustion engine. Therefore, only such a setting of the resonance point cannot sufficiently inhibit resonance of the dual mass flywheel.
In JP-A-2005-54601 (on pages 5 to 9 and FIGS. 2 to 5), in the case that the engine speed of the internal combustion engine is retained at the resonance rotational speed range for a specified period, fuel supply is stopped or reduced to control so that the engine speed of the internal combustion engine is retained out of the resonance rotational speed range. In JP-A-2006-183484 (on pages 3 to 5 and FIG. 2), the maximum fuel injection amount at the engine speed that is lower than the idling speed is limited to not more than the maximum fuel injection amount at the idling speed.
However, there are cases that such techniques cannot effectively inhibit resonance depending on the operating state of the internal combustion engine or the output transmitting state of the drive-train. In other words, there are cases that the resonance inhibiting process delays when deceleration is rapidly made in the internal combustion engine for a vehicle and therefore strong resonance may occur. Further, the resonance rotational speed differs according to the gear position of a transmission that transmits the output to the drive-train of the internal combustion engine. Therefore, strong resonance may occur in certain gear positions since the resonance inhibiting process works too late. In the other gear positions, conversely, the resonance inhibiting process works too quickly and thus reduces the output of the internal combustion engine more than necessary. This may result in an engine stall.